1. Field of the Invention
The present invention relates to an elastic roller and a method of grinding the same (hereinafter, simply referred to as “method of grinding”), more specifically to an elastic roller used for various roller material in an image forming apparatus such as copying apparatus, printer, and facsimile apparatus and the like, and a method of grinding the elastic roller.
2. Related Art
In image forming apparatuses using electrophotographic system such as copying apparatus, printer, and facsimile apparatus of an electrophotographic system, elastic rollers applied conductivity such as, transfer roller, developing roller, toner supply roller, conductive roller, cleaning roller, intermediate transfer roller, belt drive roller, etc. are used for each process in image forming. In order to obtain desired roller performance, high dimensional accuracy, surface accuracy, run-out accuracy and so on are demanded in such elastic rollers.
Such elastic rollers typically have a structure including an elastic layer carried on the outer circumference of the shaft via adhesive agent, and rubber or resin is used for the material of the elastic layer. Furthermore, foam elastic rollers using expanded rubber or resin foam are also widely used for the elastic layer, especially, the most typical one is a polyurethane foam roller which the elastic layer is constructed by polyurethane foam.
When manufacturing the elastic roller, usually an elastic layer is formed in cylindrical shape by mold-making, injection molding, extrusion molding, etc., and then the surface of the molded elastic layer roller is ground and its ends are cut in order to secure accuracy. Thus, for the purpose of preventing the elastic layer from remaining and the shaft from being damaged, there are some cases that an area where is not applied adhesive agent is provided on ends, which are cut portions, of the elastic layer, for example, as disclosed in Japanese Published Unexamined Patent Application No. H9-29843. In addition, since the elastic layer is sometimes disturbance during assembling a cartridge, for the purpose of making the elastic layer end movable, there are some cases that an area where is not applied adhesive agent is provided at the ends.
However, in case that an unapplied area of adhesive agent is provided at the ends of the elastic layer, when the surface of an elastic layer 1 is ground, as shown in FIG. 3, there are some cases in which the elastic layer 1 is pressed by a grindstone 10 at an unapplied area of adhesive agent A from the beginning of the grinding process, so that the elastic layer 1 is ground with being significantly lifted up from a shaft 2, which results in less diameter of the unapplied area of adhesive agent A than a target size. This causes problems that a uniform roller diameter in shaft direction could not be obtained, so that run-out accuracy is degraded. A numeral 20 in the figure shows supporting members of the shaft 2.
Meanwhile, to solve this problem, when the surface of the elastic layer 1 is ground, a technique in which the grind speed at the unapplied area of adhesive agent A is made slower than other areas so as to enhance processing accuracy to obtain a roller having a uniform roller diameter in shaft direction and high run-out accuracy is proposed, however, this method has a problem of poor production efficiency due to longer processing time.
When a roller having poor diametric accuracy and run-out accuracy is used, for example, for a toner supply roller in the electrophotographic process, a developing roller is not uniformly supplied with toner in shaft direction as well as that extra toner which has not been supplied from the developing roller to a photoconductor drum is not uniformly scraped in shaft direction, which results in the cause of poor image quality. Accordingly, for the elastic layer having the unapplied area of adhesive agent at the end, there has been a demand for a technique which can carry out a surface grinding with keeping high run-out accuracy and uniform diameter, and furthermore, does not reduce production efficiency.